Tottenham Court Road has been cordoned off. Armed police are attending the scene and police have sent a hostage negotiator, however police say it is unclear if there are any hostages with the man, reported to be 50-year-old Michael Green.

Police did not confirm or deny there were any snipers at the scene, saying: "It's not a matter than we ever discuss but we always deploy appropriate police resources to any incident."

People near the scene have reported shots being fired and that computers and equipment has been thrown out of the windows of the office block.

According to Abby Baafi, 27, the head of training and operations at Advantage, a company which offers HGV courses, said the man had targeted her offices and was currently holding four men hostage. She told The Huffington Post UK: "He just turned up, strapped up in gasoline, gasoline cylinders. Basically he threatened to blow up the offices. Says he doesn't care about his life, doesn't care about anything."

"He was specifically looking for me but I said 'My name's not Abby' and he let me go."